1. Field of the Invention
The present invention relates to a damper that has a magnetic fluid and suppresses vibration from occurring.
2. Description of the Related Art
A magnetic fluid (MR fluid (magneto-rheological fluid), MCF fluid (magnetic composite fluid) and so on) is a solution in which, in a solvent, fine particles of high-permeability α-Fe having particle diameters in the range of from 1 to several μm are uniformly dispersed. The fine particles of iron and the solvent such as water and oil do not separate because surfaces of ferromagnetic fine particles are processed with a surfactant. When a magnetic field is applied to the magnetic fluid, the respective particles are magnetized and form chain-like clusters aligned in a direction of the magnetic field; the clusters generate the flow resistance of the fluid; and an increase in the apparent viscosity of the entire fluid results.
The magnetic fluid is used in a damper 110 constituted, for instance, as shown in FIG. 1. In FIG. 1, a piston 113 is immersed in a magnetic fluid 116, and, owing to the viscosity between the piston and the magnetic fluid, vibration of the piston is attenuated. A static magnetic field is externally applied with an electromagnet 120. The reason for the magnetic fluid being used in the damper is that when the strength of the magnetic field applied to the damper is varied with the electromagnet 120, the viscosity of the magnetic fluid can be varied, and thereby the characteristics of the damper can be controlled. Since the damper can be controlled owing to the control of the magnetic field, the dampers with the magnetic fluid are used in seismic control devices for controlling such as earth quake and so on.
However, in the damper with the magnetic fluid, there is a problem in that, with time, the magnetic particles contained in the fluid settle. Accordingly, magnetic fluids whose particles settle with difficulty are in development.
The object of the present invention is to provide a damper in which, irrespective of the kind of the magnetic fluid, magnetic particles are difficult to settle.